1. Field of the Invention
The present invention relates to novel tetrahydropyrido[4,3-d]pyrimidines and their salts of the formula: ##STR2## as described further below. These compounds are novel, and are useful in the treatment of gastrointestinal diseases, specifically as cytoprotective agents useful in the prevention of ulcer formation.
2. Description of the Prior Art
A 4-acetyl-2-(substituted benzoyl)piperidinone has been prepared by Gruppo Lepetit as described in J. Med. Chem. 28, 934 (1985) and in U.S. Pat. No. 4,500,525 (Feb. 19, 1985). This compound was used as an intermediate to prepare pyrazolo[4,3-c]pyridines which possess antihypertensive activity, as shown in the formula below. ##STR3##
Derwent Publication Number 78-46841A/26 describes pyridopyrimidinones of the formula ##STR4## which have antidepressant and diuretic activity. In these compounds, R.sub.2 may be an aryl group or a heterocycle.
Derwent Publication Number 78-42059A/23 describes 2-amino-8-arylidene-hexahydro-4-aryl-pryidopyrimidines of the formula ##STR5## which are useful as central nervous system depressants, particularly muscle relaxants. In these compounds, R.sub.4 may be an aryl group, pyridyl group or thienyl group.
Derwent Publication Numbers 66-21740F/00, 66-13509F/00 and 66-12353F/00 describe tetrahydropyrido[4,3-d]hydroxypyrimidines of the formula ##STR6## which are useful as antiphlogistics, diuretics, antipyretics, sedatives and coronary vasodilators.